1. Field of the Invention
The present invention relates to a method for adjusting a resistance-gage force transducer.
The invention is also directed to a resistance-gage force transducer which is adjusted in particular by means of the method aforesaid.
2. Description of the Prior Art
Transducers of the above-mentioned type are already known in which one end of a resilient metal bar is attached to a stationary support and the other end is subjected to the force to be measured. This force is usually applied to a plate which is parallel to the bar and connected to this latter at the end remote from the stationary support.
The fixed bar carries resistance-type strain gages which are electrically connected to each other and form a measuring bridge for delivering an electrical signal which is a function of the force applied to the plate aforesaid.
Depending on the point of application of force on the plate, said force gives rise to variable torsional and flexural couples which act on the bar to modify the value of the electrical signal delivered by the measuring bridge and thus impair the accuracy of measurement of this force.
In consequence, appropriate steps should be taken to make this measurement insensitive to the parasitic couples just mentioned, thereby ensuring that the signal delivered is constant irrespective of the point of application of the force on the plate.
Two methods are at present in use for ensuring insensitivity of measurement of force with respect to the parasitic couples aforesaid.
In a first method, the plate rests on a system of levers which summates the forces applied to the plate and transmits the resultant force on a predetermined point to the measuring device.
In a second method, the plate is attached directly to a transducer which is often of highly complex shape so designed as to minimize the effect of the parasitic couples or moments. The transducer is usually adjusted by means of mechanical actions in order to eliminate residual effects of the parasitic moments.
In the method described in French patent No. 82 20040, an attempt has been made to solve the difficulties noted in the foregoing by eliminating the parasitic torsion signal generated at the time of application of force on the plate by means of one or a number of torsion strain gages and additional resistors of suitable design which are inserted in the signal-processing circuit.
However, this method does not permit elimination of the parasitic signal which is related to the displacement of the point of application of the force in a direction parallel to the axis of the resilient bar.